Warm compression specs are 142-199psi, and after proper valve shimming I measure 145 on both sides. Being on the low end of the range concerns me, especially with only 15k miles. Questions:

(1) Does this mean I have either burnt valves and/or damaged piston rings?
(2) Knowing that re-jetting can add a bit more power, what's the likelihood I'll damage the engine if the answer to the above is yes?

I've got readings like that before, I'd not worry too much about it. Its likely it was loose as a mofo when it left the factory.
Rejetting is for better driveability and for ease of use, and extending its life. Not always for power.
Just keep an eye on oil level and keep it clean and filled. Should make it to the 60-80K range probably.

Cool.
Buddha.